The share of public school expenditures spent on teacher salaries has declined over the last century

Dan Goldhaber and  Dick Startz:

If you go back 100 years, more than half of school spending went to teacher salaries. Where the data ends—just before the start of the COVID-19 pandemic—the fraction going to teacher salaries had fallen to a quarter. Basically, schools are spending more money, just not on teacher salaries. As an example, Chad Aldeman tells us that over a 20-year period, per-pupil revenue doubled (after inflation) but employee salaries rose only 5%. In other words, school districts have opted to increase staffing rather than increasing teacher salaries.

Teacher salaries as a share of total public school expenditures